FRP TUBULAR POLES WITH PARTIAL CONCRETE FILLING

FRP tubes have a great potential to be used as utility and light poles. Research on hollow thin-walled FRP tubular poles subjected to bending has shown that ultimate strength is governed by local buckling failure of the tubes on the compression side, prior to achieving the full strength of FRP. As such, the material is underutilized, unless a thicker wall is used, which is rather costly. Using a concrete fill inside the tube provides a low cost solution of the local buckling problem; however, complete filling of the tube is unnecessary as the pole is essentially a cantilever subjected to maximum moment at the base and zero moment at the tip. For this reason a tubular pole with partial concrete filling in the lower part only, near the base, is considered more effective. The optimum length of the concrete fill is investigated through testing of several poles of various lengths of the concrete fill. It is hypothesized that the optimum length is governed by reaching flexural material failure of the FRP tube at the base, simultaneously with local buckling failure occurring at a section above the concrete fill. This was validated experimentally and the optimum length of partial concrete fill of the tube used in this study was 38% of the full length.